Defibrillators

Claim 1

A defibrillator apparatus comprising a capacitor, charging means including a direct current source arranged to charge the capacitor to a given energy level, an inductance, and a pair of electrodes for connection by switching means to said capacitor, one by way of said inductance, whereby the capacitor may be discharged through a patient by means of the electrodes to inflict an electric shock on that patient, the selection of the energy level, the capacitor and the inductance being such that the voltage wave-form, across the electrodes, of the discharge pulse has a duration of between ten and sixteen milliseconds, a peak value of not more than four kilovolts and a minimum rise time to that peak of one thousand microseconds when the electrodes are connected across a load resistance of between 50 and 75 ohms representative of a patient, said rise time being not less than one thousand one hundred microseconds, said capacitor having a capacitance value of fifty microfarads, said inductance having an inductance value of 50 millihenries and an ohmic resistance value of 18 ohms, said means for charging the capacitor comprising a storage battery of cells, an oscillator arranged to be driven from that battery to produce an A.C. voltage output, a rectifier and voltage multiplier circuit connected to the oscillator to produce the required voltage for charging the capacitor to said energy level and a relay arranged to connect one plate of the capacitor either to said voltage multiplier circuit or to one of said electrodes, and wherein when said one plate of the capacitor is connected to said one of the electrodes, the voltage multiplier circuit is also connected to that electrode by way of a series resistor.